One of the gripes that we have seen a lot of is the fact that a shield doesn't really do much for a character until they have some experience under their belt, almost to the point of being useless. I have seen several alternatives thrown around and, while considering the authors' rationale behind how shields work, I thought of a middle ground (I doubt I am the only person who thought of this or something similar!);
Make a shield a single point of passive defense against attacks from the front. i.e. when attacking a shield bearer from the front you effectively lose 1 skill point. So, if your skill is 14, you need a 13 to hit the shield bearer. In BRP terms this is the equivalent of a 5% passive defense, and is also basically how shields worked in old school D&D by improving AC by 1. If you choose to parry with the shield you loose the passive defense for the rest of the round, reseting when new initiative cards are drawn.
Simple to implement and makes shields just a little more useful while not throwing the balance off. Thoughts?